The present invention relates to a safety device for monitoring charging of an electrical energy store of a motor vehicle and a method for operating a safety apparatus for monitoring charging of an electrical energy store in a motor vehicle.
In motor vehicles with internal combustion engines, most control devices can be switched off after as short a run-down time as possible when the vehicle is parked. In contrast, in the case of electric vehicles, a new operating state, in comparison with vehicles with internal combustion engines, supervenes the charging of the batteries.
In particular, electric vehicles or hybrid vehicles, so-called plug-in hybrids, have an energy store which can be recharged from the electrical grid. Vehicles such as this have a grid connection for recharging the electrical energy store, often in the form of a plug-in connection. During the charging process, the motor vehicle is connected to a voltage supply via a charging cable.
DE 10 2010 062 369 A1 describes a charging device without potential isolation for motor vehicles: having a first switchable isolating device which is designed to open and/or to close at least the conductor through which current flows of a charging cable that couples the charging device to a supply grid, in order to produce or break potential isolation between vehicle ground and neutral conductor of the charging cable.
Furthermore, the charging device described in that document has a second switchable isolating device which is designed to open and/or to close at least one line which connects the vehicle high-voltage battery to the charging device and/or to a vehicle onboard grid; and a monitoring device which is designed to monitor a fault state of the charging device or of the motor vehicle and to transmit a corrective signal to the first and/or second isolating device on the basis of the fault state.
DE 10 2009 001 962 A1 describes a charging system for use in a vehicle with vehicle ground at earth potential, comprising a vehicle high-voltage grid containing a high-voltage battery with battery isolation device and optionally one or more consumers; a charging device which is conductively connected to the high-voltage battery and can be integrated in the vehicle and has a grid isolating device which is connectable to a charging grid via a grid plug.
The charging system described in that document also comprises one or more residual current circuit breakers for monitoring residual current during a charging process, wherein the residual current circuit breakers are arranged such that the charging system is isolatable from a connected charging grid via the residual current circuit breakers, a protective conductor which is connectable to the vehicle ground, and means for permanently monitoring the protective conductor function during a charging process, wherein the means are configured such that, if the protective conductor function is impaired, the battery isolating device of the high-voltage battery and the grid isolating device of the charging device are triggerable.
Moreover, in the charging system described in that document, means are provided for isolation monitoring of the vehicle high-voltage network and of the charging device before the start of a charging process, wherein the means are configured such that, if an isolation fault is detected, the battery isolating device of the high-voltage battery and the grid isolating device of the charging device are triggerable.